The Standard Lexical Sets for English introduced by John C. Wells in Accents of English are in wide usage. Wells defined each lexical set on the basis of the pronunciation of words in two reference accents, which he calls RP and GenAm.[1]

"GenAm" refers to an accent of the General American type, which is associated with a geographically "neutral" or widespread sound system throughout the US.[3]

Wells classifies words of the English language into 24 lexical sets on the basis of the pronunciation of the vowel of their stressed syllable in the two reference accents. Each lexical set is named after a representative keyword, as follows:[4]

For example, the word rod is pronounced /rɒd/ in RP and /rɑd/ in GenAm. It therefore belongs in the LOT lexical set. Weary is pronounced /ˈwɪərɪ/ in RP and /ˈwɪri/ in GenAm, and thus belongs in the NEAR lexical set.

Some words of the English language do not belong to any lexical set. For example, the a in the stressed syllable of tomato is pronounced /ɑː/ in RP, and /eɪ/ in GenAm, a combination which is very unusual, and is not covered by any of the 24 lexical sets above.[5]

The keywords have been chosen in such a way that clarity is maximized: whatever accent of English they are spoken in, they can hardly be mistaken for other words. Although fleece is not the commonest of words, it cannot be mistaken for a word with some other vowel; whereas beat, say, if we had chosen it instead, would have been subject to the drawback that one man's pronunciation of beat may sound like another's pronunciation of bait or bit.[4]

Wells also describes three sets of words based on their word-final unstressed vowels. Although not included in the standard 24 lexical sets, these "have indexical and diagnostic value in distinguishing accents".[6]

The Standard Lexical Sets of Wells are widely used to discuss the phonological and phonetic systems of different accents of English in a clear and concise manner. Although based solely on RP and GenAm, the Standard Lexical Sets have proven useful in describing many other accents of English. This is true because, in many dialects, the words in all or most of the sets are pronounced with similar or identical stressed vowels. Wells himself uses the Lexical Sets most prominently to give "tables of lexical incidence" for all the various accents he discusses in his work. For example, here is the table of lexical incidence he gives for Newfoundland English:[7]

KIT

ɪ

FLEECE

iː

NEAR

ɛr

DRESS

ɛ

FACE

ɛː, ɛɪ

SQUARE

ɛr

TRAP

æ

PALM

æ, ɑː

START

ær

LOT

ɒ

THOUGHT

ɑː

NORTH

ɔ̈r

STRUT

ɔ̈

GOAT

ʌʊ

FORCE

ɔ̈r

FOOT

ʊ

GOOSE

uː

CURE

ɔ̈r

BATH

æ

PRICE

əɪ

happY

[i]

CLOTH

ɑː

CHOICE

əɪ

lettER

ər [ɚ]

NURSE

ɜr

MOUTH

əu

commA

ə

The table indicates that, for example, Newfoundland English uses the /ɪ/ phoneme for words in the KIT lexical set, and that the NORTH, FORCE and CURE sets are all pronounced with the same vowel /ɔ̈r/. Note that some lexical sets, such as FACE, are given with more than one pronunciation: this indicates that not all words in the FACE lexical set are pronounced similarly (in this case because Newfoundland English has not fully undergone the pane–pain merger).[8] (Note that in 1982 Wells used an older version of the International Phonetic Alphabet which lacked many of the independent symbols for central vowels. 1982 /ɔ̈/ was the open-mid central rounded vowel, which today is /ɞ/.)

Wells also uses the Standard Lexical Sets to refer to "the vowel sound used for the standard lexical set in question in the accent under discussion":[9] Thus, for example, in describing the Newfoundland accent, Wells writes that "KIT and DRESS are reportedly often merged as [ɪ]",[10] meaning that the stressed syllables of words in the KIT lexical set and words in the DRESS lexical set are reportedly often pronounced identically with the vowel [ɪ].

I sometimes think that a century from now my lexical sets will be the one thing I shall be remembered for. Yet I dreamt them up over a weekend, frustrated with the incoherent mess of symbols used in such contemporary publications as Weinreich's "Is a structural dialectology possible?".[11]

He also wrote that he claimed no copyright in the Standard Lexical Sets, and that everyone was "free to make whatever use of them they wish".[11]

Some varieties of English make distinctions in stressed vowels that are not captured by the 24 lexical sets. For example, some Irish and Scottish accents that have not undergone the fern–fir–fur merger split the NURSE lexical set into multiple subsets. For such accents, the 24 Wells lexical sets may be inadequate. Because of this, a work devoted to Irish English may split the Wells NURSE set into two subsets, a new, smaller NURSE set and a TERM set.[12]

Some writers on English accents have introduced a GOAL set to refer to a set of words that have the GOAT vowel in standard accents but may have a different vowel in Sheffield[13] or in south-east London.[14] Wells has stated that he didn't include a GOAL set because this should be interpreted as an allophone of GOAT that is sensitive to the morpheme boundary, which he illustrates by comparing the London pronunciations of goalie and slowly.[15]